Renal calcium conservation in recurrent stone-formers with idiopathic hypercalciuria

Urinary excretions of calcium and cyclic AMP were studied in male recurrent stone-formers after an overnight fast and following an oral calcium load. The results from eight patients with established hypercalciuria (greater than 7.5 mmol Ca/24 h) were compared with those from eight age matched normocalciuric stone-formers. The urinary calcium/creatinine ratio was higher in the hypercalciuric group both when fasting and calcium loaded whilst their urinary cyclic AMP was lower in both 24-h and calcium-loaded collections. Five of the eight hypercalciuric patients exhibited an increased urinary calcium/creatinine ratio whilst fasting. These findings support the view that renal calcium wasting, in association with suppression of parathyroid activity, is common among men with idiopathic hypercalciuria. Dietary calcium restriction may lead to bone loss in patients with obligatory renal calcium wasting and enteric adsorption is rarely applicable to the treatment of stone disease. Therefore, the demonstration of a high fasting urinary calcium/creatinine ratio is a strong indication for therapeutic agents which act to suppress renal calcium loss to treat hypercalciuria.